Production of organic xanthogen sulfides



P. F. WARNER ETAL 2,839,560 PRoDucTIoN oF ORGANIC xANTHoGEN suLFIDEs June 17, 1958 Filed May 9, 1955 2 Sheets-Sheet 1 Filed May 9, 1955 2 Sheets-Sheet 2 INVENTORS P. F. WARNER A.D. ADAMS 8 9 OM REACTION ZONE I l I ANTHOGEN) TR|sULF|DE M REACTION zoNE v. AQuEous PHASE SE FRO VAILABLE XANTHATE IN ETHYLX s PHA OF AQUEOU pH OF AQUEOUS PHASE FR PREPARATION OF Dl er* 9 N ZONE B OM REACTIO 4 7 y pH OF AQUEOUS PHASE FR United States Patent O PRODUCTION OF ORGANIC XANTHOGEN SULFIDES Paul F. Warner and Archie D. Adams, Phillips, Tex., assignors to Phillips Petroleum Company, a corporation of Delaware Application May 9, 1955, Serial No. 506,857 15 Claims. (Cl. 26o- 455) This invention relates to the production of organic xanthogen suldes. In one aspect this invention relates to the production of organic Xanthogen suldes by reacting an aqueous solution of an alkali metal xanthate or an ammonium Xanthate with a chloride of sulfur. In another aspect this invention relates to controlling the rate of yaddition of at least one of said reagents to a reaction zone responsive to the pH of an aqueous phase in said reaction zone.

Organic Xanthogen suldes can be prepared by the reaction of alkali metal Xanthates or an ammonium xan- In the so-callcd dry process a slurry of the Xanthate, preferably an alkali met-a1 xanthate, in an organic solvent is prepared. After the slurry is prepared, the sulfur chloride is then added, with stirring, at a controlled rate, i. e., as rapidly as the evolution of exothermic heat will permit and still maintain the temperature in the reaction zone at the desired level. The mixture is stirred for about 5` to 30 minutes after addition of the sulfur chloride is complete. The product is generally washed with water and dried. In the so-called wet process, an aqueous solution of the Xanthate, preferably an Ialkali metal xanthate, is iirst prepared, and an organic solvent is then added. The sulfur chloride is then introduced at a controlled rate with constant stirring of the reaction mixture. The reaction is exothermic and the addition of the sulfur chloride is controlled at a rate such that the temperature can be maintained at the desired level. Stirring is generally continued for 5 to 30 minutes after addition of the sulfur chloride to allow time for further reaction. At the` conclusion of the reaction the aqueous and organic solvent phases are separated. The organic solvent phase is washed with water and dried. Methods of preparation of various organic Xanthogen sullides fand the use of same as plant defoliants are disclosed and claimed in co-pending application Serial No. 388,684, tiled October 27, 1953. The above described wet process, i. e., whereinl an aqueous solution of the Xanthate is employed, is a presently preferred process Iand the present invention relates to an improvement in said process.

As mentioned, the reaction between alkali metal Xanthates and sulfur chlorides is exothermic and in the prior art it has been customary to control the rate of yaddition of the reagents to each other so as to control the exothermic heat of reaction. In the above-described wet process an aqueous phase and an organic solvent phase are present in the reaction zone. We have found that when the pH of the aqueous phase in the reaction zone is maintained at a predetermined value between 7 and 8 an increased yield of 4the reaction` product is obtained. More ecient utilization of the reagents yand less corrosion of the processing equipment are also obtained when the pH is maintained within the above said limits. We have also found that the pH of the aqueous phase in the reaction zone can be controlled by controlling the rate of addition of at least one of the said reagents. We have further found that the addition of the reagents to the reaction zone can be conveniently and advantageously controlled responsive to the pH of the aqueous phase in the reaction zone.

An object of this invention is to provide an improved method for the production of organic Xanthogen suldes.

Another object of this invention is to provide an improved method for reacting an aqueous solution of an alkali-metal Xanthate or an ammonium Xanthate with a chloride of sulfur to produce an organic Xanthogen sulfide of improved quality in increased yield.

Another object of this invention is to control the rate of `addition of at least one reagent to a reaction zone, in a system wherein an aqueous solution of an alkalimetal Xanthate or an ammonium Xanthate is reacted with a chloride of sulfur, responsive to the pH of the aqueous phase in said reaction zone.

Still another object of this invention is to reduce and/or eliminate corrosion in a system wherein an alkali-metal Xanthate or an ammonium Xanthate is reacted with a chloride of sulfur.

Still another object of this invention is to provide a method for reacting an aqueous solution of an alkalimetal xanthate or an ammonium xanthate with a chloride of sulfur whereby more eflicient utilization of said reagents is effected.

Other aspects, objects and advantages of the invention will be apparent to those skilled in the art upon reading this disclosure.

According to the invention there is provided a process for the preparation of Xanthogen triand tetrasultides which comprises reacting an aqueous solution of an alkali metal xanthate and/or an ammonium Xanthate with a chloride of sulfur in ya reaction zone and maintaining the pH of the aqueous phase in said reaction zone at a predetermined Value within the range of 7 to 8.

The organic Xanthogen sulfides which can be prepared according to our invention can be represented by the formula wherein R is selected from the above named group of organic radicals which R and R are selected from and M is selected from the group consisting of sodium, potassium, lithium, rubidium, caesium and ammonium ion (NH4+).

Chlorides of sulfur which can be used according to our invention include sulfur monochloride, S2Cl2, and sulfur dichlorde, S012. When sulfur dichloride is used the reaction product is predominantly the trisulde. When sulfur monochloride is used the reaction product is predominantly the tetrasullide. Mixtures of the two said chlorides of sulfur will result in a mixed product, the ratio of the tri-sulfide to the tetrasulfde in the product being proportional to the amounts of the said chlorides `of sulfur in the starting reagent.

Typical organic Xanthogen suldes which can be prepared from the corresponding Xanthates according to our invention include dimethylxanthogen trisulide, dimethyl- Xanthogen tetrasulde, diethylxanthogen trisulde, di-

ethylxanthogen tetrasullide, di-n-propylxanthogen trisuliide, di-n-propylxanthogen tetrasulfide, diisopropylxanthogen trisulde, diisopropylxanthogen tetrasulde, di-tert-butylxanthogen trisulde, ethyl-tert-butylxanthogen tetrasulfide, methylethylxanthogen trisuliide, methylethylxanthogen tetrasuliide, ethylphenylxanthogen trisulde, phenylbenzylxanthogen trisulfide, methylcyclohexylxanthogen tetrasulfide, ethylhexylxanthogen vtrisulfide, methylhexylxanthogen tetrasulde, methyldecylxanthogen trisulde, di-n-octylxanthogen trisulde, di-ndecylxanthogen trisulide, and the like.

Figure l is a diagrammatic flow sheet of the process of the invention.

Figure 2 is a graph showing the correlation between the pH of the aqueous phase in the reaction zone and product yield.

Figure 3 is a graph showing the correlation between the pH of the aqueous phase in the reaction zone and the amount of available unreacted xanthate in said aqueous phase.

Referring now to the drawings, and particularly to Figure 1, the invention will be more fully explained as applied to the manufacture of diethylxanthogen trisulfde. An aqueous solution of sodium ethyl xanthate,approxi mately 34 percent by weight, is irst prepared in mixing vat and transferred via pump 11 and line 12 to xanthate solution tank 13. Xanthate solutions is then pumped by means of pump 14 via line 15 through line 61, reactor pump 16, line 17, separator 18, line 19, cooler 20, and line 60. Pump 16, line 17, separator 18, line 19, cooler 20, line 61B and line 61 comprise the reaction zone. After circulation is thus established in the reaction zone, flow of organic solvent (described further hereinafter) is started from solvent storage tank 21 via pump 22, and line 23 into said reaction zone. The rate of iow of said organic solvent is controlled by motor valve 25 responsive to rate of ow controller 26. Plow of sulfur dichloride from weigh tank 27 via metering pump 24 and line 28 into said reaction Zone is then started. Upon starting flow of the organic solvent valves 29 and 30 are opened. Upon starting the flow of the sulfur dichloride solution the temperature in the reaction zone rises to about 94 F. and isrmaintained at about this point by means of cooler 29. During the reaction a small amount of gas is formed which is vented through valve 30 and line 31. A mixture of `organic phase and aqueous phase is withdrawn from gas separator 18 via line 32 and passed into phase separator 33. In said phase separator the aqueous phase and organic phase separate, the aqueous phase being withdrawn through line 34 and motor valve 35 responsive to liquid level con- Cil troller 36. A sample of the aqueous phase in line 34 is continuously withdrawn and passed through pH recording controller 37 which is operatively connected to motor valve 38 in line 15. pH recording controller 37 is set to control the rate of addition of xanthate solution to the reaction zone responsive to the pH of the aqueous phase in line 34 by means of motor valve 38 and to maintain the pH of said aqueous phase at a predetermined value between 7 and 8.

Organic solvent phase is withdrawn from phase separator 33 via line 39 into surge tank 40. Said organic solvent phase containing the reaction product dissolved therein is pumped by means of pump 41 and line 42 into the bottom of scrubber 43 wherein it is contactedv countercurrently with water introduced through line 44. Scrubber 43 is preferably a packed vessel containing a packing such las Berl saddles, Raschig rings, etc. Scrubbing water is withdrawn from the bottom of scrubber 43 via line 45 controlled by motor valve 46 responsive to liquid level controller 47. The ratio of the volume of scrubbing water to the volume of organic solvent is usually about 1:1; however, lower and higher ratios can be employed. Scrubbed organic solvent containing the reaction product dissolved therein is removed overhead from scrubber 43 and passed via line 48 into surge tank 49 from which it is pumped by means of pump 50 and line 51 through water trap 52 from which it passes via line S3 into drier 54. Drier 54 can be filled with any suitable drying agent which is non-reactive with the reaction product or the organic solvent. Bauxite, due to its ready availability and low cost, is a presently preferred drying agent. Dried organic solvent containing the reaction product is withdrawn from drier 54 through line 55 and stored in product storage 56.

The 'above method of preparation is particularly adapted to the preparation of solutions of organic xanthogen suldes which are to be employed as plant defoliants. By thus preparing the sulfide in the presence of a suitable solvent which can lalso serve as the carrier for the sulfide defoliating agent, a finished defoliant which can be stored and shipped as such is obtained.

Itis necessary, periodically, to regenerate the bauxite in drier 54. This can be done, Ias in well known to those well skilled in the art, by passing a stream of gas, such as natural gas, flue gas etc., through line 57, heater 58 and line 59 into drier 54 to remove the water absorbed lby the drying 'agent therein. While only one drier has 'been shown it will be understood by those skilled in the art that two or more such driers, suitably manifolded in parallel so as to provide for at least one drier on stream at all times, can be employed.

TABLE I during preparation of di(ethylxanthogen) trsulyde Run No l 2 i 3 4 5 Solvent Feed Rate, G. P. HJ 25.5 29. 9 34. 7 33. 7 26.0 Sulfur Dichlorde Feed Rate, lb./hr 36. 3 34.8 34. 2 34. 8 36. G Xanthate Solution Feed Rate, G. P. H l 26. 2 28.0 25. 5 28. 2 24. 9 Concentration of available Xanthate in solution, wt, percent 33. 3 3l. 30. 30. 5 29. 3 Specific Gravity of Xanthate Solution, gm ml- 1.1880 1. 1869 1.1866 1. 1868 1.1854 Reactor Pump Outlet Temp., F 94 93 90 95 93 Cooler Outlet Temp., F 89 94 Reaction Zone Water Phase, pH 7. 7 7. 4 7. 6 Available Xanthate in Water Phase,

percent 2. 6 0. 1 0.0 Water to Scrubber, G. P. HJ 60 60 Product Solution Refractive Index, 'rt/2 1.4724 1.4807 1.4787 Product Solution Specic Gravity, 20/20 0.8731 O. 8937 0.8902 Product Solution Concentration:

wt. percent 30.1 32.0 26. 6 31. 4 30. 2 lb./gal 2. 21 3. 38 1.90 2. 32 2...!1 Product Rate,z G. P. HJ 31.9 37.8 42. 9 42. 9 32. 4 Yield, based on Available Xanthete, Wt. percent of theoretical 77 88 92 100 85 l Gallons per hour. .2 Calculated from product solution concentration and solvent feed rate.

The aqueous phase from phase separator 33 is representative of the aqueous phase in the reaction zone. It is to be noted that the pH of said 4aqueous phase is maintained at a predetermined value within the range of 7 to 8, preferably within the range 7.0 to 8.0, more pref erably within the range 7.2 to 7.6, When the pH of the aqueous phase is above about 7.6 the yield of the organic xanthogen sullide decreases and all of the available xanthate is not being'consumed in the reaction. When the pH of said aqueous phase drops to 7 or below excessive foaming and gas evolution occurs and an oil phase which is heavier than water is produced. The yield of the desired sulfide is also low when the pH is below 7.

Table I above summarizes operating conditions and yields obtained in five different runs wherein sodium ethylxanthate and sulfur dichloride were reacted to prepare di(ethylxanthogen) trisullide.

Figure 2 is a graph showing correlation between the pH of the aqueous phase in the reaction zone and the product yield.

The data given in Table I and Figure 2 represent the results of runs made to determine the optimum pH at which to maintain the aqueous phase in the reaction zone. Other' runs had indicated the necessity for maintaining said pH above about seven and below about eight. Said other runs had definitely shown that if the pH of the aqueous phase in the reaction zone was above eight, the yield of sulfide was low and all the available xanthate was not being consumed in the reaction; if the pH was below seven excessive foaming and gas evolution would occur and an oil phase that was heaver than water would be produced causing a reduction in yield. Said foaming and gas evolution also interrupted circulation within the reaction zone. v

It is to be noted from a Table I and Figure 2 that tained at a pH of about 7.4 to 7.5.

Another outstanding advantage of our invention is that, when the pH of the aqueous phase in the reaction zone is maintained at a predetermined value within the range of 7 to 8 the quantities of the reagents present in said zone are substantially stoichiometrically balanced, and there is substantially complete utilization of both reagents. Both reagents are relatively expensive. Further, there is no convenient practical method for the recovery of unreacted reagents from the reaction product, Therefore, the economic advantages of our invention, in addition to the previously discussed increased product yield and quality, will be readily appreciated by those skilled in the art. Figure 3 illustrates the marked savings which can be realized, with regard to the xanthate, when operating according to `our invention.

A still further advantage of our invention is that ordinary corrosion resistant materials of construction such as 310 stainless steel, 316 stainless steel, Monel metal, Hastelloy B and Hastelloy C, can be employed. When the pH of the aqueous phase is not maintained at least above 7.0 non-metallic materials of construction must be employed.

The sodium ethylxanthate employed in the above runs was a commercial product and had the following approximate analysis.

comparison of the data in the maximum yield was ob- Components: Weight percent Sodium ethylxanthate 84.5 Sodium sulfide 1.7 Sodium thiocarbonate 3.4 Other (by diiference):

Sodium carbonate Sodium sulfite 10.4 Sodium thiosulfate The sulfur dichloride employed in the above run was a Gravity, API at 60 F 51.2 Aromatics, vol. percent 0.00 Paraiiins-f-naphthenes, vol. percent 98.6 Bromine number, electrometric method 1.2

Total sulfur, wt. percent 0.0017

Aniline number, F 210 Distillation, ASTM D86-46: IBP F 428 5 percent 432 10 do 433 20 do 435 50 do 439 90 do 446 do 448 D. P 450 E. P 462 Other organic solvents can be employed in the process of our invention. Solvents which are generally preferred, particularly when the suliides are to be used as defoliants, are paratlinic hydrocarbons. Single hydrocarbon compounds or mixtures can be used. Suitable parafinic hydrocarbons include those of relatively low boiling point, such as propane, butanes, pentanes and hexanes. Of particular interest are the highly branched isoparaiiinic hydrocarbons, containing from 9 to 20 carbon atoms per molecule, having boiling points in the range between 260 and 800 F. These materials can be obtained from any suitable source. Convenient methods` for their preparation include alkylation of isoparatiins with monoolelins, using catalysts such as hydrogen iiuoride, aluminum chloride, sulfuric acid, or the like. However aromatic solvents are not excluded. The choice of organic solvent to be used will depend to a large extent on the use to be made of the sulde product and whether or not said product is to be used in solution or recovered from the solvent. The amount of solvent used is generally suiiicient to give a product concentration of from 2.0 to 2.5 pounds per gallon of solvent. However, quantities of solvent above and below this amount can be employed.

The temperature in the reaction zone is usually maintained within the range of 40 to 140 F., preferably within the range of 90 to 110 F.

Suiiicient pressure is employed to maintain the solvent in liquid phase.

Approximately 2 mols of the Xanthate are usually employed per mol of the sulfur chloride. In general, the amount of xanthate used isin the range between 1.5 and 3, preferably between 1.8 and 2.5, mols per mol of the sulfur chloride. `Although the rate of addition of either reagent to the other can be controlled according to the invention, it is presently preferred to sety and maintain the sulfur chloride feed rate substantially constant, and then vary the feed rate of the xanthate solution so as to maintain the pH of the aqueous phase in the reaction zone within the range of 7.0 and 8.0 as described above.

It is theoretically possible to analyze each feed stream and then calculate the amount of each to be used in order to maintain the properV ratio of reactants in the reaction zone. However this approach to the problem is entirely impractical in continuous commercial operation because neither of the feed streams are pure material. The sulfur dichloiide has a specification of 66 percent minimum chlorine content which represents about a 95 percent solution of sulfur dichloride. However, the sulfur dichloride is somewhat unstable and easily reverts to the sulfur monochloride making it almost impossible to determine and know the composition of the stream at all times in continuous operation.

Furthermore, xanthate solutions react slowly with water and unless some provision such as that provided by our invention is made an error in the amount of xanthate can occur. As pointed out above it is very desirable to maintain the pH of the aqueous phase in the reaction Zone within relatively narrow limits for maximum eiciency of the process. Thus the advantages of our invention, which provides a method for realizing the maximum efficiency of the process will be readily apparent to those skilled in the art in view of this disclosure.

While in this specification and in the claims the terminology employed is considered applicable, the compounds prepared according to the invention can be called dixanthogen triand tetrasulides, as indicated by the formula given herein therefor. Also, the employ of parenthesis is possible in the names of the compounds, for example, di(ethylxanthogen) trisultide.

As will be evident to those skilled in the art, various modifications of the invention can be made, or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

We claim:

1. A process for the preparation of an organic xanthogen suliide which can be represented by the formula F. an aqueous solution of a xanthate represented by the formula wherein R can contain from 1 to 10 carbon atoms and is selected from the above named group of organic radicals and M is selected from the group consisting of sodium, potassium, lithium, rubidium, caesium, and arnmonium, with a chloride of sulfur selected from the group consisting of sulfur monochloride and sulfur dichloride, by continuously adding a stream of said xanthate and a stream of said chloride of sulfur to a reaction zone in the presence of an organic solvent capable of dissolving said organic xanthogen suldes, measuring the pH of the resulting aqueous phase in said reaction zone, and adding and reacting said reagents in substantially stoichiometrically balanced amounts by controlling the rate of addition of one of said reagents responsive to the pH ot said resulting aqueous phase in said reaction zone, so as to maintain the pH of said aqueous phase within the range of 7 to 8.

2. A process according to claim l wherein the rate of addition of said solution of said Xanthate to said reaction zone is controlled so as to maintain said pH within the range of 7.0 to 8.0.

3. A process according to claim 1 wherein the rate of addition of said chloride of sulfur to said reaction zone is controlled so as to maintain said pH within the range of 7.0 to 8.0. 4

4. In a process for the preparation of a di(alkylxantho gen) trisulde having from 1 to l0 carbon atoms in each alkyl group wherein an aqueous solution of an alkalimetal xanthate is reacted with sulfur dichloride in a reaction zone at a temperature within the range of 40 to 140 F. in the presence of an organic solvent capable of dissolving said tri-sulfide and wherein there exists in said reaction zone an aqueous phase and an organic solvent phase, the improvement which comprises continuously adding a stream of said xanthate and a stream of said sulfur dichloride to said reaction zone, measuring the pH Vs of said aqueous phase, and adding and reacting said reagents in substantially stoichiometrically balanced amounts by controlling the rate of addition of one of said reagents to said reaction zone responsive to the pH of said aqueous phase, so as to ma1ntain the pH of said aqueous phase within the range of '7 to 8.

5. A process according to claim 4 wherein said Xanthate is sodium ethyl xanthate and the rate of addition of said xanthate to said reaction Zone is controlled so as to maintain said pH within the range of 7.0 to 8.0.

6. A process according to claim 4 wherein said Xanthate is potassium ethyl xanthate and the rate of addition of said xanthate to said reaction Zone is controlled so as to maintain said pH within the range of 7.0 to 8.0.

7. A process according to claim 4 wherein said xan- 4 thate is sodium ethyl xanthate and the rate of addition of said sulfur dichloride is controlled so as to maintain said pH within the range of 7.0 to 8.0.

8. A process according to claim 4 wherein said Xanthate is potassium ethyl xanthate and the rate of addition of said sulfur dichloride is co-ntrolled so as to maintain said pH within the range of 7.0 to 8.0.

9. In a process for the preparation of a di(alkylxantho gen) tetrasulde having from one to ten carbon atoms in each alkyl group, wherein an aqueous solution of an alkali-metal Xanthate is reacted with sulfur monochloride in a reaction Zone at a temperature within the range of 40 to F. in the presence of an organic solvent capable of dissolving said tetra-sulfide and wherein there exists in said reaction zone an aqueous phase and an organic solvent phase, the improvement which comprises continuously adding a stream of said xanthate and a stream of said sulfur monochloride to said reaction zone, measuring the pH of said aqueous phase, and adding and reacting said reagents in substantiallyk stoichiometrically balanced amounts by controlling the rate of addition of one of said reagents to said reaction Zone responsive to the pH of said aqueous phase, so as to maintain the pH of said aqueous phase within the range of 7 to 8.

10. A process according to claim 9 wherein said xanthate in sodium ethyl xanthate and the rate of addition of said xanthate to said reaction zone is controlled so as to maintain said pH within the range of 7.0 to 8.0.

11. A process according to claim 9 wherein said xanthate is potassium ethyl xanthate and the rate of addition of said xanthate to said reaction zone is controlled so as to maintain said pH within the range-of 7.0 to 8.0.

12. A process according to claim 9 wherein said Xanthate is sodium ethyl xanthate and the rate of addition of said sulfur monochloride is controlled so as to maintain said pH within the range of 7.0 to 8.0.

13. A process according to claim 9 wherein said Xanthate is potassium ethyl xanthate and the rate of addition of said sulfur monochloride is controlled so as to maintain said pH within the range of 7.0 to 8.0.

14, A process according to claim l wherein the pH of said aqueous phase is maintained within the range of 7.2 to 7.6.

15. A continuous process for the preparation of an organic Xanthogen sulfide which can be represented by the formula R-O-ii-s.- -0-R' wherein: R and R' are organic radicals selected from the group consisting of alkyl, cycloalkyl, aryl, alkaryl, and aralkyl groups; n is an integer which can be one of 3 and 4; R and R' can be diierent; and each R and R can contain from 1 to l0 carbon atoms; which process comprises; continuously passing to a reaction zone an aqueous solution of a xanthate represented by the' formla s R"-O\ol-SM wherein R" can contain from 1 to l0 carbon atoms and is selected from the above named group of organic radi- S H C eals and M is selected from the group consisting of sodium, patossium, lithium, rubidium, caesium, and ammonium ion; .continuously passing a solution of a chloride of sulfur selected from the group consisting of sulfur monochloride and sulfur dichloride to said reaction Zone; continuously passing an organic solvent capable of dissolving said organic xanthogen suliides to said reaction zone; maintaining said reaction zone at a temperature within the range of 40 to 140 F.; continuously circulating reaction mixture within said reaction Zone; continuously withdrawing a portion of said circulating reaction mixture from said reaction zone and passing same to a separation zone; in said separation zone effecting a phase separation between an aqueous phase and a solvent phase 10 Within the range of 7 to 8.

References Cited in the le of this: patent UNITED STATES PATENTS 1,634,924 Whitby July 5, 1927 

1. A PROCESS FOR THE PREPARATION OF AN ORGANIC XANTHOGEN SULFIDE WHICH CAN BE REPRESENTED BY THE FORMULA 